THE SHRINKAGE OF LAKE NICARAGUA 


A Question of Permanency of the Proposed Nicaragua 

Canal 

* 


by 


ANGELO HEILPRIN, F. R. G. S., F. G. S. A., 

Late President of the Geographical Society and Professor of Geology at the 
Academy of Natural Sciences, of Philadelphia, Member of 
the American Philosophical Society, etc. 


(From the Bulletin of the Geographical Society of Philadelphia) 



JULY, IQOO 











'.'ty Transfer 


II cl 90 ( 











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BULLETIN 

OF THE 

Geographical Society 

OF PHILADELPHIA 


VOL. II JULY, iqoo NO. 6. 


The Shrinkage of Lake Nicaragua. 

A Question of Permanency of the Proposed Nicaragua Canal. 


BY 

ANGELO HEILPRIN, 

Late President of the Geographical Society and Professor of Geology at the 
Academy of Natural Sciences, Philadelphia. 


A serious aspect of the proposed Nicaragua Canal, and 
one that has so far escaped earnest consideration, is that which 
pertains to the permanency of the waters of Lake Nicaragua, 
the fountainhead of the San Juan River. The canal for which 
it is intended to use the lake as the feeder to its high level must 
necessarily have this permanent, and if it cannot be held so, 
there can be no permanent canal. In a paper published in the 
Scientific American , of February 24, 1900, entitled “An As¬ 
sumed Inconstancy in the Level of Lake Nicaragua,” and 
further elaborated in the pages of the Bulletin of the Geograph¬ 
ical Society of Philadelphia for March, “The Nicaragua Canal 
in its Geographical and Geological Relations,” I have given 
what appeared to me good reasons for believing that the level 
of the lake is inconstant, and that the waters have dropped 
from 15 to 20 feet in the period of half a century or less. 












n6 The Shrinkage of Lake Nicaragua. 

This conclusion is supported by the earlier determinations of 
altitude made by the Spanish engineer Galisteo, in 1781, and 
the English engineer Baily, in 1838, the results of which 
differ from those obtained more recently in the American sur¬ 
veys by some 20 to 30 feet. In a paper having the same 
title as my own, published in The National Geographic Maga¬ 
zine for April, Mr. C. Willard Hayes, of the U. S. Geo¬ 
logical Survey, and Geologist to the Nicaragua Canal Com¬ 
mission of 1897-99, attempts to refute my conclusions, and 
asserts that “notwithstanding these earlier determinations the 
level of Lake Nicaragua has remained constant except for slight 
seasonal fluctuations, at least for a period whose length has to 
be measured in centuries,” and “that the geologic conditions in 
this portion of the Isthmus are such that they afford a promise 
of future stability, and that the region is, therefore, favorable for 
the construction and maintenance of a work such as the pro¬ 
posed Nicaragua Canal” (p. 161L Mr. Hayes concedes that a 
region subject to the change which I have indicated “would 
offer serious obstacles to the construction of a canal of the mag¬ 
nitude of the one proposed or to its permanency after con¬ 
struction ” (p. 156). 

A critical examination of Mr. Hayes’s premises shows them 
to be far from convincing, while the data presented in the 
official report of Chief Engineer Wheeler, of the Nicaragua 
Canal Commission, effectually dispose of his contention as to 
the lake’s stability, and confirm the argument which has been 
advanced for its instability. Mr. Hayes gives three causes, 
singly or in combination, * ‘ which might bring about a change 
in altitude of the lake surface: (1) A depression of the whole 
of this portion of the Isthmus without warping; (2) a depression 
of the lake basin by warping, the sea margins remaining con¬ 
stant; (3) a cutting down of the lake outlet” (pp. 156-7). 
Not finding direct evidences of these causes, the case is con¬ 
sidered to have no standing. 


Angelo Heilprin. 


117 

To many geologists, other causes beside the three that have 
been brought forward will suggest themselves as being able to 
bring about the result which has been indicated, and in a way 
equally as simple and effective as those which Mr. Hayes 
names. Of such, one need hardly go beyond the very obvious 
one of a shrinkage in the supply of inflowing water.* 

It is hardly necessary to traverse the arguments, based 
upon characteristics of flood-plains, the presence or absence of 
lake beaches and terraces, shore deformations, etc., upon which 
Mr. Hayes relies to prove the non-existence of his three causes ; 
geologists know how illusory are “landmarks” of this kind in 
their negative condition. Nor need any particular weight be 
attached to the testimony of observations made or not made on 
the local phenomena by the inhabitants of a region, the partic¬ 
ular history involved in which dates to a period of fifty or 
sixty years back. When one realizes how many years were 
required to prove and disprove the difference of level of the 
two oceans on the opposite sides of the Isthmus of Panama; to 
prove and disprove the rise and fall of the land on the northern 
shore of the Bay of Naples in the classic ground of the Temple 
of Serapis; to prove and disprove that Mount Hood, a vol¬ 
cano standing almost on the outskirts of a populous town, was in 
energetic eruption in 1875 ; to prove or disprove that the famous 
Calaveras skull was found where it was found, etc., one need, 
perhaps, hardly assent to the proposition that in a region like 
Nicaragua some of its more pregnant phenomena “could not 
possibly escape notice” f, and that lacking observational facts 


* In a future paper I shall discuss the subject of the engulfment of the lake and the 
nature of the Rivas plain. 

f When in 1890 I announced, as the result of my barometric observations, that Ixtac- 
cihuatl, a mountain standing only 40 miles from the city of Mexico, measured in height 
little short of 17,000 feet, instead of being 15,600 feet, the statement was met with the 
proper objection, that if the mountain in reality was so close a competitor with Popo¬ 
catepetl, the fact would have been noted long before—more particularly, as the two 
mountains formed part of the special study of Alexander von Humboldt during his resi¬ 
dence in the Mexican capital. 



n8 The Shrinkage of Lake Nicaragua. 

indicating an abasement of the waters of the lake, none such 
could have taken place. As a matter of fact, however, bearing 
upon the condition of Lake Nicaragua, emphatic testimony to 
the lowering of its waters is given by the English engineer Col- 
linson, who ran a partial survey in the region in 1867 ; and in 
his report to the Royal Geographical Society, he further states 
that “even the least observant native, dwelling on the lake, will 
tell how its banks are rising year by year visibly before his eyes, 
etc.,” and, thereby, whether accurately or inaccurately, supple¬ 
ments his own observations by an appeal to the observation 
of native sources. It is hardly necessary at this time to inquire 
into the credentials which Mr. Collinson bore as an engineer; 
suffice it to say, that there is enough evidence to show that in 
his day, whether his researches in Nicaragua were correctly or 
incorrecdy made, he was considered a very competent observer; 
and his conclusions regarding the lake appear to be abundantly 
confirmed by the data furnished in the special report of the Chief 
Engineer, appended to the official report of the Nicaragua Canal 
Commission of 1897-99. 

From this report it is made very plain that the intake of 
Lake Nicaragua, i. <?., the rainfall on its surface and the water 
that it receives from its full drainage basin, is for a run of years, 
and apparently for almost every year, less than the output, i. e., 
the loss due to evaporation and outflow. Indeed, in exception¬ 
ally dry years, the evaporation alone more than covers the entire 
intake.* From the observations made at a number of stations 
on the lake, it would appear that the annual rainfall over its 
surface is within about 28 per cent, of that at Rivas, while the 
inflow collected from the enclosing drainage basin is somewhat 
less than this amount, or 30 per cent, of the full rainfall over 
a region that has an area about three times that of the lake.f 

* “During the dry season, the evaporation exceeds the inflow. During exceptionally 
dry years, exceeds the inflow for the entire year.” Report Chief Engineer Wheeler, p. 58. 

t Report Nicaragua Canal Commission, page 19. 



Angelo Heilprin. 


119 

These data, with a knowledge of the amount of evaporation and 
the outflow, permit of an easy determination of the hydrodyna¬ 
mics of the lake. The evaporation from the surface of the lake 
is stated to be on an average 6 inches per month during the 
dry season, and 4 inches in the wet. In 1898, the full evapora¬ 
tion for the year was 52 inches, but that year was considered to 
be “an abnormally wet one, and it is, therefore, probable that 
the evaporation was somewhat below the average. Mr. Davis 
(the hydrographer of the commission) estimates a normal annual 
a gg re g a t e at about 60 inches, or 5 feet.”* 

The following absolute rise in the level of the lake as com¬ 
puted from a possible rainfall at Rivas is furnished by the engi¬ 
neers of the Canal Commission : 

A rainfall of 30 inches would cause a rise, were there no 

evaporation or overflow, of. 34 inches. 

A rainfall of 40 inches do do. 48 “ 


it 

a 

50 

it 

a 

ii 

. 63 

ii 

i i 

a 

60 

it 

<< 

11 

. 78 

i i 

it 

a 

70 

t i 

<( 

ii 

. 93 

i i 

ii 

i t 

80 

ii 

(< 

a 


a 

it 

a 

90 

ii 

«« 

it 

.125 

a 

i ( 

a 

100 

it 

tt 

ii 

. 141 

a 

a 

a 

no 

ii 

a 

ii 

. 157 

a 

a 

t < 

120 

ii 

i i 

ii 

. 175 

i t 

a 

a 

130 

it 

a 

it 

.192 

11 


From November 1, 1889, to June 1, 1891, a period of 19 
months, the total rainfall at Rivas was 38*39 inches, which would 
have raised the level of the lake 45*75 inches. The evaporation 
alone during this time would have lowered it 95 inches,f an ab¬ 
solute loss to the lake, beyond what would be entailed by the 
outflow through the San Juan River, of over 4 feet. This, it 
is true, was the driest period observed, but the condition is said 
to be “not at all anomalous.” From the beginning of Decem¬ 
ber, 1884, to the end of April, 1886, a period of 17 months, the 


* Report Nicaragua Canal Commission, page 18. 
t Report Chief Engineer, page 66. 

























120 The Shrinkage of Lake Nicaragua. 

total rainfall at Rivas was 37*43 inches, which amount would raise 
the level of the lake 44*4 inches. The evaporation for the same 
period is assumed to have been 84*25 inches, a net loss to the 
lake from this source alone of 3 feet 4 inches. From the be¬ 
ginning of November, 1894, to the end of April 1896—19 
months—the rainfall was 45*15 inches, which would put a credit 
of 55*72 inches to the lake. The evaporation for the same 
period was 95 inches, a loss to the lake again of 3 feet 4 inches. 
The loss to the lake during three dry spells, calculated from the 
excess of evaporation over rainfall and inflow, and without taking 
count of the natural outflow through the San Juan River, was, 
therefore, 10 feet 10 inches. The report judiciously and signifi¬ 
cantly adds : ‘ ‘ The recurrence of such dry years shows that 

they are to be expected in the future and should be provided 
for.”* 

It is self-evident that unless there are special compensations 
to the lake for such losses, the losses must be perpetual; and the 
compensations sought for can only be found in years or periods 
of extraordinarily heavy rainfall. The problem of restoration, 
therefore, rests entirely with the question of such periods occur¬ 
ring or non-occurring. The reports of the Chief Engineer and 
Hydrographer of the Canal Commission plainly state that they have 
not occurred. 

Despite the fact that following rapidly on excessive rains the 
surface of the lake has been known to rise as much as two feet 
in six weeks, the greatest net accession to the lake for an entire 
year, and through a period of 20 years, was considerably less 
than two feet. This was in the year 1897, when the rainfall at 
Rivas during the 164 days between May 17 and October 27, was 
112*42 inches,—“the period of greatest rainfall shown in the 
Rivas records since 1879. . . . This then (148*58 inches) is 

the estimated amount of fluctuation that would have occurred 


Report Chief Engineer, page 66. 



Angelo Heilprin. 


121 


during the period of greatest rainfall of the last 20 years, if there 
had been no evaporation on the lake or overflow from it.”* 

The year 1898, when the rainfall at Rivas was 108 inches, 
was almost, or quite, as favorable as 1897, and the net rise in 
the lake was 18 inches. The evaporation from the lake was 
during the year 52 inches, and the outflow through the San Juan, 
84 inches—the lake, therefore, throwing off 11 feet 4 inches. 
Had there been no evaporation or outflow, the lake would have 
risen that year 154 inches, f Taking the outflow of 84 inches 
to be about normal for the lake standing at, or but little above, 
mean stage of water—elevation 104 to 106 feet—with a steady 
evaporation of from 50 to 60 inches, it is made impressively 
clear that many successive years of heaviest rainfall would be 
required to make good the deficiency of a single exceedingly dry 
period ; and, if such cannot be had, there must be steady, pro¬ 


gressive and non-recuperative losses to the lake. This condi¬ 
tion is, in fact, very plainly indicated in the report on rainfall by 
Mr. Arthur P. Davis, appended as the hydrographic report to 
the general report of the Nicaragua Canal Commission (1899). 


The following yearly record of rainfall at Rivas, noted by Dr. 
Earl Flint for the years 1880-1898, is there given (pp. 278-79) : 


1880 

1881 

1882 

1883 

1884 

1885 

1886 

1887 

1888 

1889 

1890 

1891 

1892 

1893 

1894 

1895 

1896 

1897 

1898 


64*38 inches. 
79'2i 
61*32 
4977 
5474 
34*59 
87*21 
74*89 
55*5i 
84*36 

31*81 
66*03 
78*27 
106*13 
47*32 
47*68 

47*8o 
123*43 
108 *06 


* Report Nicaragua Canal Commission, page 21. 
f Report Nicaragua Canal Commission, page 19. 























122 


The Shrinkage of Lake Nicaragua. 


If with a rainfall of 108 inches, as before referred to in the 
year 1898, the net rise of the lake was only 18 inches, it be 
comes manifest from an examination of the above table and 
that before furnished for correspondent rises in the lake, that 
during 19 years of successive observations there were not more 
than three (or at the utmost four) periods, the years 1893, 1897 
and 1898 (and 1886?) when the lake held its own; and during 
these years combined, the actual gains were less than five feet. 
On the other hand, in the single year of 1890, when the rainfall 
at Rivas was only 31*81 inches, the loss was as great as the 
gains for the entire 19 years ! 

Not knowing the amount of outflow through the San Juan 
River for the different years from 1880 to 1898, but assuming it, 
for a simple convenience of measure, to be on an average not 
more than one-half the amount,* 84 inches, that was found for 
the year 1898, and taking the annual evaporation at 55 inches- 
we arrive at the following interesting analysis of the table of 
rainfall: 


In 1880 

the lake lost . . 

. . 12 

inches 


“ 1881 

44 

4 4 

gained 



10 inches 

“ 1882 

a 

44 

lost . . 

• 17 

44 


“ 1883 

44 

44 

lost . . 

• • 34 

44 


“ 1884 

44 

44 

lost . . 

• 27 

44 


“ 1885 

(( 


lost . . 

• • 55 

44 


“ 1886 

44 

44 

gained 



2i « 

“ 1887 

a 

44 

gained 



3 “ 

“ 1888 

44 

44 

lost . . 

• • 27 

44 


“ 1889 

a 

44 

gained 



19 

“ 1890 

4 i 

44 

lost . . 

. . 61 

44 


“ 1891 

a 

44 

lost . . 

. . 11 

44 


“ 1892 

44 

4 4 

gained 



8 

“ 1893 

44 

4 4 

gained 



11 

“ 1894 

44 

44 

lost . . 

. .40 

44 


“ 1895 

4 4 

4 4 

lost . . 

. . 40 

4 4 


“ 1896 

44 

44 

lost . . 

• -39 

44 


" 1897 

44 

44 

gained 



24 (-f) “ (as determined) 

“ 1898 

44 

44 

gained 



18 “ “ “ 


_ 363 inches 114 inches 

• Except for the years 1893, 1*97 and 1898. 







Angelo Heilprin. 


123 


A loss ol 363 inches as against a gain of 114 inches, or a 
net loss of 249 inches (20 feet 9 inches). The amount that I 
have allowed for outflow is probably fully 20 per cent, less than 
what was actually the case, if the data obtained by Childs in 
1850, the Nicaragua Canal Board in 1895, and the Nicaragua 
Canal Commission in 1898-99, be assumed as the basis for com¬ 
putation, and I have taken the small measure merely to allow 
every advantage in favor of the argument for a maintenance of 
level. The evaporation assumed is also 5 inches less than what 
is assumed to be the amount for an average year by Mr. Davis. 

It thus becomes apparent that for a long period of years 
Lake Nicaragua has undergone a very marked and progressive 
shrinkage; and there is nothing to indicate that the loss involved 
in this shrinkage can be made good for future years. If it is 
possible to assume other periods of years when the rainfall may 
be vastly in excess of what has been recorded for the past 
twenty years and more, and that a balance can be restored in 
this way, it can only be said that there is no evidence of such 
successive periods of excessive rainfall ever having taken place; 
and we may quote the words of Mr. C. Willard Hayes : “So 
far as known there is no evidence whatever that the rainfall has 
ever been greater in this region than it is at the present time;”* 
and further, “it is, therefore, impossible for the level of the 
lake to reach the elevation given by Lieut. Baily, merely by 
reason of heavy precipitation. ”f 

Conclusions. 

The full conclusions, then, that must be drawn from the data 
furnished by the Nicaragua Canal Commission of 1897-99, and 
the special reports of the Chief Engineer and Hydrographer ap¬ 
pended thereto, are : 


* Official report Nicaragua Canal Commission, page 145. 
f National Geographic Magazine, April, 1900, page 161. 



124 


The Shrmkage of Lake Nicaragua. 


1. Lake Nicaragua has undergone marked shrinkage during 

the period of the last 25 to 50 years. 

2. The shrinkage is a progressive one, and there are no 

known conditions by which the loss incurred can be 
made good. 

3. The assumption is well founded that the earlier measure¬ 

ments of the altitude of the lake surface, made by Gal- 
isteo and Baily, indicating an abasement of the waters 
by 20 to 30 feet, were accurate. 

The relations of these conditions to canal construction become 
immediately apparent, and it may well be agreed that a region 
subject to the changes which have been indicated “would offer 
serious obstacles to the construction of a canal of the magnitude 
of the one proposed or to its permanency after construction.” 





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